Answer
This scenario presents an essential troubleshooting problem often asked in Class 1 exams. Specific Fuel Oil Consumption (SFOC) is measured in grams per kilowatt-hour (g/kWh).
Total Fuel Consumption (MT/Day)=Engine Power (kW)×SFOC (g/kWh)×24 Hours
If SFOC remains perfectly within its design parameters, the thermodynamic and mechanical efficiency inside the engine cylinders is normal. The elevated daily fuel consumption (MT/Day) means the engine is being forced to produce significantly higher Power (kW) to maintain the desired ship speed.
Extraneous Factors Causing High Power Demand:
Severe Hull and Propeller Fouling: Micro-fouling (slime/algae) and macro-fouling (barnacles/tubeworms) exponentially increase the vessel's hydrodynamic resistance, requiring more shaft power to overcome hull drag.
Adverse Weather and Environmental Conditions: Sailing against heavy head-seas, high wind resistance, or strong counter-currents increases the ship’s hull wake fraction and resistance.
Unfavorable Trim and Draft (High Displacement): Operating the vessel at a trim that is not optimized for the current draft increases the wetted surface area, creating wave-making resistance.
Shallow Water Effect (Squat): When sailing through restricted or shallow waters, the return flow of water around the hull creates a pressure drop, causing the ship to "squat." This alters the hull resistance parameters, making the vessel harder to propel.
High Auxiliary Load / Shaft Generator Drag: If the vessel utilizes a Shaft Generator (PTO - Power Take-Off) to supply the ship's electrical grid, any massive increase in electrical demand (e.g., running cargo conditioning plants on an LPG/VLGC carrier, or heavy ballast pumps) places a direct mechanical torque drag on the Main Engine, requiring more fuel injection to maintain set RPM.